Some people are at risk of having a heart attack or stroke due to fatty plaque buildups in their arteries that restrict the flow of blood or even break off and block the flow of blood completely. Angioplasty is a procedure for treating sites that are affected by plaque. In this procedure, a needle is used to make an opening through a patient's skin and into a blood vessel, often the femoral artery in the patient's leg. A sheath is used to hold the opening open and a radiopaque dye is injected, allowing physician view the treatment site on x-ray and select a suitable balloon catheter and a guidewire for treatment.
The guidewire is then inserted through the hole and guided through the artery until the tip just passes the treatment site. The physician guides the wire by twisting and manipulating the proximal end that sits outside the patient. With the wire in place, the balloon catheter is slid over the proximal end and pushed forward until the balloon lies within the narrowed area. The balloon is then inflated to compress the plaque or to deliver a stent.
A number of problems are associated with this procedure. For example, in places where the guidewire lies against the side of the vessel, pushing the catheter over the guidewire can scrape the catheter against the vessel wall. The guidewire tends to be pushed against the vessel wall by any curve in the vessel. Specifically, the guidewire will push against the inside wall at the peak of the curve and against the outside wall at the ends of the curve.
Curves also present navigational challenges. For example, where a curve in the vessel lies close to a branch-point, it can be difficult to guide the tip of the wire into the correct branch due to the strong tendency of the curve to push the wire towards one side of the vessel.
Some positioning difficulties could be helped by an imaging guidewire. For example, a guidewire with an ultrasound imaging tip could help a physician navigate the vessels. However, the tendency of the guidewire to push up against the vessel wall interferes with imaging. If the imaging device is pushed into the vessel wall, it will not be useful for viewing its environment.